Invalid number error in where clause - sql

Question

I am executing a query in Oracle database. The column and everything is correct but I am getting an Invalid Number error for below query:
select COUNT(*) AS "COUNT" from NE.STRUCT B
where B.STRUCT_TYPE in ('IDC')
and NET_ENTITY_ID is not null
and length(NET_ENTITY_ID) = 18
AND regexp_like(SUBSTR(NET_ENTITY_ID,15,1),'[^A-Z]')
and TO_NUMBER(SUBSTR(NET_ENTITY_ID,(length(NET_ENTITY_ID) -3), 4)) < 6000;
NET_ENTITY_ID field has only one data ABCDEFGHXXXXNB0001.
But not necessary that it will always be having one data. This is just for resolving the issue I am considering only this.
Error Message:
ORA-01722: invalid number
01722. 00000 - "invalid number"
*Cause: The specified number was invalid.
*Action: Specify a valid number.

Answer 1

The problem is that Oracle -- and any other database -- does not guarantee the order of evaluation of clauses in a WHERE. You can get around this using CASE:
where B.STRUCT_TYPE in ('IDC') and
NET_ENTITY_ID is not null and
length(NET_ENTITY_ID) = 18 AND
regexp_like(SUBSTR(NET_ENTITY_ID, 15, 1), '[^A-Z]') and
(CASE WHEN regexp_like(SUBSTR(NET_ENTITY_ID,(length(NET_ENTITY_ID) -3), 4), '^[0-9]{4}$'
THEN TO_NUMBER(SUBSTR(NET_ENTITY_ID,(length(NET_ENTITY_ID) -3), 4))
END) < 6000;

Answer 2

You need to ensure that the last 4 chars are numeric before using TO_NUMBER on them.
This will do it:
select COUNT(*) AS "COUNT" from
( SELECT * FROM NE.STRUCT B
where B.STRUCT_TYPE in ('IDC')
and NET_ENTITY_ID is not null
and length(NET_ENTITY_ID) = 18
AND regexp_like(SUBSTR(NET_ENTITY_ID,15,1),'[^A-Z]')
AND regexp_like(SUBSTR(NET_ENTITY_ID,-4),'[0-9]')
)
where TO_NUMBER(SUBSTR(NET_ENTITY_ID,-4)) < 6000;
NB I simplified your SUBSTR for obtaining the last 4 characters.